99 silverado with tach that bounces

[maccbell]

I have a 99 1/2 ton silverado with 112,000 miles on it. For the last six months the truck feels like it misses around 50 mph. The tach will bounce and it is easily felt. Had it looked at and the #8 cylinder was showing a miss and the plug was still white eventhough it had been changed about 9 months ago. The EGR valve had a leak so we replaced that but didn't solve the problem. I was wondering if anybody else has had this problem and what it is?

[j cAT]

Originally Posted by maccbell

I have a 99 1/2 ton silverado with 112,000 miles on it. For the last six months the truck feels like it misses around 50 mph. The tach will bounce and it is easily felt. Had it looked at and the #8 cylinder was showing a miss and the plug was still white eventhough it had been changed about 9 months ago. The EGR valve had a leak so we replaced that but didn't solve the problem. I was wondering if anybody else has had this problem and what it is?

the pcm gets engine rpm info from crank sensor. when sensor starts to go if your lucky it will cause your problems. soon it will die after warm up and when it cools it may run again for a day or so. of course if it were my engine i would measure resistance, and check wires . then i would buy new sensor and compare with old . very high or open and the sensor is bad...... should read 3k-5k ohm range i have seen the tach jump to max rpm to zero rpm it sometimes will not be felt while driving.